I was recently involved in a discussion on a sister site regarding how tightly coupled Physics is with the age of the Universe (and Earth).

I believe that the Earth and the Universe are both billions of years old, but don't know enough on why exactly other than having confidence in peer reviewed science. Moreover, it would be helpful if I knew which parts of physics are tightly coupled with the current age estimate. So,

Are there any notable hypotheses or entire fields of modern physics that both:

do not rely on the age of the Earth for their predictive and explanatory power and

do not predict an old Earth

If so, which fields depend (directly or indirectly) on the age of the Earth, and which do not?

Put differently,

consistent with old Earth = hypotheses that either rely on the age of the Earth for their predictive power or predict an old Earth

M = Modern physics.

Mo = Modern physics consistent with old Earth.

Mn = Hypotheses that both do not rely on the age of the Earth for their predictive power and do not predict an old Earth.

Then M = Mo∪Mn. My question is if there are any hypotheses in Mn, or Mn is an empty set?

5 Answers
5

$M_0$ is all of physics (the serious one); $M_n$ is virtually all of physics, except for cosmology and geophysics (and some other "historical sciences" I don't want to enumerate in too much detail because it's just a matter of terminology and most of them don't naturally belong to physics, anyway).

An overwhelming majority of physics (the Standard Model of particle physics, nuclear physics, atomic physics, biophysics, physical chemistry, optics, electromagnetism, condensed matter physics, hydrodynamics, aerodynamics, thermodynamics, and dozens of others) doesn't rely on the age of the Earth or age of the Universe. Most of physics is concerned with the description of local processes that can be observed in some region and in some relatively short enough period of time. Most of physics extracts observations of local, short-lived processes and objects; and after they're evaluated, it makes statements about the local and short-term behavior of the physical systems, too. Those things don't depend on whether or not the Earth is old or the Universe is old. By this I mean that if we lived in a hypothetical Universe in which the observations of the Earth or the Universe would imply that those entities are much younger, much older, or infinitely old, but the lab experiments would proceed just like in our world, almost all of physics would work just like it does in our world.

With this being said, physics also provides us with the most powerful tools that make it obvious that both the Earth and the Universe are billions of years old – if we want to answer this question. We know that we don't live in the hypothetical world. However, to do so, we must couple the physical laws or gadgets offered by the local physics (i.e. those that depend on local and short-term observations and the theories "induced" out of them) with some particular observations – such as the observation of radioactive isotopes or the outward motion of other galaxies from us. When we find the age of the Earth and the Universe, it's obviously very important for the disciplines that study the history of the Earth and the Universe but it's not important for the rest of physics – which is still an overwhelming fraction of physics.

Of course, one may also choose to "overlook" all the evidence that implies that the Earth and the Universe are billions of years old (or, alternatively, "deny" the local theories of physics that are also needed to prove that the Earth and Universe are old). But it's just not right for a scientist to overlook evidence. He or she may only be "less interested in it" than in some other questions. I think that a way to reformulate your question so that it would sound much more scientific is to ask What is the actual evidence that the Earth and the Universe are billions of years old. One could discuss the evidence, its strength, and perhaps some loopholes (I am not really aware of). But it does seem to me that the OP doesn't really intend to discuss the evidence at all; the question seems to be more about why don't we just completely deny this evidence.

As the patient posters (unsuccessfully) tried to explain to the OP on the Skeptics stack exchange, the age of the Earth and the age of the Universe aren't "assumptions" of physics in any sense; the situation isn't analogous to religion where similar claims may be part of the axioms codified by a holy scripture. In physics, they're just two inevitable consequences of the physics research and some particular useful observations – aside from many other consequences that physics has. Much like physics implies that the transistor behaves in a particular way, it implies (together with the observations of distant galaxies) that the Universe is 13.73 billion years old. It just happens that the latter statement is more inconvenient from the viewpoint of those who cherish certain old traditions (I mean religious ones).

I was also the OP on the Skeptics, motivated by a claim that "[were Earth 6000 years old] all 20th century physics would be very wrong". I accept that all things taken together, evidence for Earth and Universe being billions of years old is overwhelming. But I am not comfortable with a statement that says if that was not the case, then all modern physics would be wrong. I am not after denialism - I just don't like blanket statements which don't seem truthful.
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ipavlicApr 10 '12 at 11:34

Dear @ipavlic, as written above, I agree that most of physics doesn't depend on the ancient Earth or the ancient Universe; these two numbers (ages) aren't assumptions of physics in any sense. Your scenario "if that was not the case, then all modern physics would be wrong" is ill-defined, however. We don't live in world that doesn't contain proofs that the Earth is old. So you're talking about some hypothetical other world which is very different from ours. Properties of this hypothetical other world can only be settled if you tell us more about that world. There's no "universal answer".
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Luboš MotlApr 10 '12 at 11:37

In particular, one may think about a hypothetical different world where lab phenomena behave just like here but where the Earth is just 6,000 years old - and can be shown to be this young. After all, this is how our world looked like 4.7 billion years ago, too. In that world, the young age of the Earth is actually right and could be scientifically justified. However, there's no world in which the observations are completely identical to ours but which prevents us from proving that the Earth is old. If such a world were possible, we could prove the same thing here, too. But we know we can't.
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Luboš MotlApr 10 '12 at 11:40

If you don't like the statement "all of 20th century physics is all about the ancient Earth/Universe", I completely agree with you. It's not a right statement. Only a very small portion of the physics research was affected by or did affect those questions. Still, this portion of the research and evidence exists. To make science compatible with the young Earth/Universe, one wouldn't have to change "all observations or all insights" in physics, just a relatively small percentage. It's still impossible to "change" this subset of observations. They have already been done and tell us what they do.
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Luboš MotlApr 10 '12 at 11:46

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Thank you for your clarifications. It seems to me that I understand the issue a little better now. If I may be so bold, it also seems that we are approximately on the same page on this issue.
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ipavlicApr 10 '12 at 11:48

I don't think it's possible to answer your question in any useful way.

For example, I spent 12 years working as a colloid scientist, and I don't recall having to take the age of the earth or indeed the universe when I was trying to calculate the shelf life of a bottle of shampoo. However the interparticle forces in colloids are described using the same quantum mechanics that describes radioactive decay, and radioactive decay is one of the main ways to calculate the age of rocks.

So is colloid science linked to the age of the Earth? Well, it depends on your point of view. I would say the answer was yes, because I see science as an integrated whole. It's very hard to break just one bit of it without affecting all the other areas of science.

Our estimate of the age of the universe depends on general relativity, and it's possible that GR is only approximately correct so the age could be greater or smaller than we think. However it would be hard for GR to be very wrong without affecting other systems we can observe like pulsar binaries, so again you get cross checks with other areas of physics and our calculated age of the universe isn't likely to be far out.

Yes, by my definition, I would say that colloid science is linked to the age of Earth for precisely the same reasons that you stated (QM background). Is there any field of modern physics that does not rely on either QM or GR (or QM+GR = modern physics)?
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ipavlicApr 10 '12 at 9:36

Everything ultimately depends on QM or GR. There is no branch of science (not just physics) that cannot in principle, though not usually in practice, be reduced to some combination of QM and GR.
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John RennieApr 10 '12 at 9:40

While surgery could be reduced to QM and GR, that is not ever done. I'm guessing we could say that surgery is independent on the age of the Earth because: 1) it doesn't rely on the age of the Earth for predictions 2) it doesn't predict the age of the Earth. The same would probably hold for mathematics, non-molecular biology, and some parts of chemistry. If nothing better comes up, I'll accept your answer.
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ipavlicApr 10 '12 at 9:47

What you say about surgery applies equally to colloid science, but we've just agreed that colloid science is linked to the age of the earth. As for biology, a reductionist (and I apologise here to the many biologists I know) would argue that biology is applied molecular biology, which is applied chemistry, and chemistry is applied physics. The "reduce everything to physics" gets a bit silly after a point, but an error in QM severe enough to get the age of the earth wrong would affect pretty much everything around us.
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John RennieApr 10 '12 at 9:57

The distinction for me is that you actually use equations from QM to work in the field of colloid science. If you graft nerves together in surgery, you don't really need to rely on any statements from QM.
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ipavlicApr 10 '12 at 11:50

(I do not specify this but it's fairly obvious that) The Omphalos hypothesis is not a scientific hypothesis and is completely irrelevant in the discussion.

If the universe were 6000 years old, yet we do observe phenomena which appear much farther away than 6000 light years, then there is something wrong with the speed of light - it can't be really as constant as assumed and it can't really work as we think it does. I think this is a pretty big problem for special relativity, general relativity and so on. See this site for a more in-depth explanation.

If radiometric dating gives wrong results (and at the moment, the age of the earth is measured through different isotopes and completely independent radiometric experiments), then our radioactive decay does not work as predicted by QM and in particular by Heisenberg's uncertainty principle. The prediction here is that $\Delta E\Delta t \geq \hbar/2$ where $\Delta E$ is related to how much energy is released with decay and $\Delta t$ related to a typical decay period. (see pag. 91 here). Obviously, if the time varies, then either the energy varies or $\hbar$ varies. They should really be constant. This puts a big dent into quantum mechanics.

Clearly if the universe if 6000 years old, the big bang did not happen 13.7 billions of years ago. This directly disproves the Big Bang theory

Again, if the universe were 6000 years old, planetary formation and in particular the solar system formation is wrong.

There's surely a bunch of physics which does not depend on QM or relativity, BUT I think it's reasonable to say that all the major (theoretical) physics that was done in the XX century does depend on one of these.

Thank you for your clarification. So young earth would imply YE→ ¬GR ∧ ¬QM, making it easier to search for such hypotheses (if they exist). I most note that it seems that in the current formulation you are addressing a bit weaker claim of major theoretical physics hypotheses. I was curious if there were any notable physics hypotheses.
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ipavlicApr 11 '12 at 7:41

@RonMaimon one could say it's "as reasonable as YEC" - which was precisely my point. The tricky bit is explaining to the OP how unreasonable that is :-)
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Sklivvz♦Apr 11 '12 at 8:10

@RonMaimon I'm not considering whether the failure of QM, GR and radioactive decay are reasonable. I'm asking whether there is anything notable in 20th century physics that does not rely on old Earth and doesn't predict an old Earth. It really is a simple question. It seems like you're making a straw man out of it.
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ipavlicApr 13 '12 at 8:31

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@ipavlic: Yes, sure--- renormalization theory (inasmuch as it is classical), dynamical systems theory (although it gives magnetic reversals in the Earth's magnetic field that are observed to go back more than 6000 years in magnetized rocks), condensed matter physics, etc. It is only in experiments that are designed to measure the age of the Earth that you see the age of the Earth. But what I'm saying is that our theories are held together well, so that if we were to discover certain evidence that the Earth is 6000 years old, everything is wrong.
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Ron MaimonApr 13 '12 at 8:39

@Sklivvz I was not positing some form of YEC. I'm asking about a much weaker statement which is not religiously-motivated: whether there is anything notable in 20th century physics that does not rely on old Earth and doesn't predict an old Earth.
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ipavlicApr 13 '12 at 8:42

I think that the following fields do not care about the age of the Earth a lot:

Conservation of momentum/Newton's laws

Statics

Thermodynamics

Some parts of EM (electrostatics)

The following fields will fall apart:

Maxwell's equations (since these predict the light from stars is long ago)

Quantum mechanics (everything goes)

Relativity (all wrong)

The way to find the cutoff is to see when physics started to date the Earth reliably--- this happened around the turn of the 20th century. So all physics before that wasn't very sensitive to the age of the Earth, and all physics after that was. It's not much more subtle than that.

In geology, the evidence for an old-Earth was found in the 19th century, same in biology. So more of those sciences fall apart, essentially all of geology and all of biology.

But physics is a bottom-up science--- the most foundational things are the ones on which everything else is built. So the young Earth, although it is wrecking "only" the last hundred years of physics, is wrecking the most foundational parts, and the parts that have withstood the most scrutiny, and which lie beneath and explain the parts that do happen to work under young Earth.

But one must remember that the adherents of young Earth basically only have a manifestly fictional book to point to, so their evidence has zero credibility. They don't believe this because they have evaluated evidence in a neutral manner.

If you wish to get rid of young Earth creationism, it is important to both respect this belief--- understand its source, and attack the beliefs at the source. Young Earth creationists don't care about Big Bang nucleosynthesis. They care about loving your fellow man. In order to love one's fellow man, one must have a system of absolute ethics, which is roughly along the lines of Hofstadter's superrationality. But extending Hofstadter's concept to asymmetric games is logically-positivistically equivalent to postulating that there is a super-smart agent which knows the right behavior in all circumstances (see this Christianity answer).

Most of these people are not completely delusional, they are only following (understandable and compelling) spiritual guidance that tells them that there is a super-smart agent in charge of ethics, that it is extremely important to inform people of this agent, and that if you have to, you lie through your teeth to get them to believe in this agent, because this trumps all other concerns. I am sure that most of these folks don't actually believe the Earth is 6000 years old, or that there was a global flood, but they are shrewd enough to know that it would be good if people followed the absolute morality, and they are sure that the only path to this absolute morality is found in the Bible.

So they lie about almost anything, including the content of the Biblical texts. This makes them not science-friendly, since science demands honesty as the first and only commandment.

These lies are not tenable in the modern media environment, but it is important in my opinion to preserve the valuable ethical lessons of the Biblical texts, and extract the logical positive essence which can be used to continue religion outside the realm of magical thinking, before cosigning the magical fantasies to the dustbin of history.

The first part of your answer answer the 1), the second part (cutoff) is great for 2), but I would like to keep it to Physics (everything from "But one must remember that..." seems superfluous to me).
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ipavlicApr 11 '12 at 7:48

I haven't thought this throug but is it possible that (eventually) changing physical laws "disprove" conservation of energy because of noether's theorem?
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Sklivvz♦Apr 11 '12 at 8:12

@Sklivvz: Noether's assumes QM is correct, or Lagrangian mechanics--- if you throw away the rest of physics, I don't see how such rarefied considerations are going to convince you. The important thing is to acknowledge that ethics really come from God, not from individual people maximizing self-interest. Once people understand this, without miracles, the miracles will wither and die.
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Ron MaimonApr 11 '12 at 15:29

I disagree with most answers here. Pretty much all branches of Physics and Laws of Physics does not depend on whether the universe is old or whether the earth is old. What would be different would be the Assumptions, Models, and currently accepted Initial Conditions if they are not so. For instance, before the discovery of the expansion of the universe the universe most scientists believe the universe has always existed. Einstein even added the cosmological constant allegedly to balance a "steady-state universe." Then the Friedman model was proposed and the expansion of the universe was verified. The Hubble constant was measured. After that, different models, assumptions, and initial conditions was proposed, but all based on the current understanding of QM and GR. Even if very strong evidence comes up that the Universe is much younger, it doesn't make sense at all to say QM and GR are incorrect. What that means is that current models, assumptions, and initial conditions are, in some, combinations, incorrect. That is why we would then need new models, assumptions, and initial conditions to explain new evidences that comes that is contrary to current understanding. That's how science works.